1. Field of the Invention
The present invention relates to a syringe, especially to a syringe that safely controls the injection dose and is laborsaving in operation.
2. Description of Related Art
In order to achieve multiple purposes such as dose metering, injection time counting, and repeatable use, the conventional syringes include two kinds: a dose metering syringe and a frequency measuring syringe. The structure of the conventional dose metering syringe mainly includes a driving device assembled by multiple driving components mounted in a barrel and connected with a piston rod. A vial is assembled in the barrel. A needle is mounted on a front end of the barrel and is connected with the vial for injection. When the syringe is in an injecting process, the needle is pierced into the skin or the veins of a human body, and the driving device is driven by pushing the piston rod to inject the medication. The dose of the injection can be controlled by the driving device and the movement of the piston rod to achieve the purpose of dose-metering.
However, the conventional dose metering syringe still has an issue of laboriousness. To solve the laboriousness issue, the conventional dose metering syringe has a structure that comprises a large pitch travel structure and a small pitch travel structure, such that the pushing force provided by a user can be effectively transformed to a rotating force. Accordingly, the operation of the conventional syringe is labor-saving.
However, an injection rod may be pulled backward during the operation of the conventional dose metering syringe, so the safety of use of the conventional syringe should be improved.
To overcome the shortcomings of the conventional dose metering syringe, the present invention provides a syringe to mitigate or obviate the aforementioned problems.